Comparative Study of the Pheromone-manufacturing Femoral Glands in Two Sympatric Species of Lacertid Lizards (Acanthodactylus)

Femoral glands are holocrine structures that produce compounds used by lizards as pheromones. Few studies have investigated the morphology and ultrastructure of these glands. We chose a closely related species pair from a lizard family having femoral glands in male and female of both species to illustrate comparative morphology and ultrastructure and their implications for the mechanism of secretion dispersal to the environment. We also aimed to test whether the structure and mechanism of secretion production differ between related species. In addition, we sought to gain a better understanding of the holocrine mechanism of secretion. Femoral glands of selected sympatric lacertid species, Acanthodactylus boskianus and A. scutellatus were studied comparatively using light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SEM revealed both interspecific and sexual variation in the morphology of the glandular pores. The external morphology suggests the mechanism of the secretion deposition where the convex part of pore-carrying scale is probably used to partition the secretory plug. Histology shows the epithelial cells of the gland duct as an extension of the epidermis with its covering keratin. The glandular acini are composed of germinal and secretory cells. The latter undergo four different stages of differentiation, from the beginning of the formation of secretory granules, through the accumulation of these granules, disintegration and formation of the secretory plug, which protrudes externally. The study considers the sequence of holocrine secretion development, and explains in part how such secretions are deposited on the substrate. Sexual differences at the external morphology level were more evident than interspecific differences.